In the oil and gas industry, chemical management can be important in optimizing fluid production, as well as in minimizing well downtime and expensive intervention. Chemical injection systems may be used to introduce chemicals into the wellbore. Chemical application may include, for example, scale inhibitors, asphaltine inhibitors, emulsions, hydrate inhibitors, defoaming, paraffin, scavengers, corrosion inhibitors, demulsifiers and the like. A typical chemical injection system may include a chemical injection mandrel interconnected along a production pipe string so that the mandrel bore is in fluid communication with the annulus of the pipe string. The mandrel may include one or more injection ports to release chemicals into the mandrel bore. One or more chemicals are supplied to the chemical injection ports via a chemical injection line extending from the surface externally along the outer surface of the pipe string. The chemical injection line extends to the surface where it is coupled to a chemical injection pumping unit. Various other control and communication lines may also extend along the external surface of the pipe string between the chemical injection mandrel and the surface control equipment. The chemical injection mandrel generally also includes a check valve positioned along the flow path to the injection port. The purpose of the check valve is to prevent wellbore fluids, such as production gas, oil or water, from migrating into the chemical injection system via the injection port.
Commonly, prior to injection of chemicals, the chemical injection system is pressure tested to ensure integrity of the chemical injection system. One of the preferred methods of pressure testing a chemical injection system is to incorporate a burst disc, tensile stud, shear pin or similar rupture mechanism at a point along the fluid flow path of the chemical injection system to allow an operator to maintain positive internal pressure within the chemical injection system upstream of the rupture mechanism, permitting the integrity of the chemical injection system to be confirmed. Upon successful pressure testing, the pressure within the chemical injection system is then increased to exceed the rating of the rupture mechanism, forcing the rupture mechanism to fail so as to open up flow through the chemical injection system.
One drawback to conventional pressure testing is that breakage of the rupture mechanism can create debris that can become lodged in downstream flow components, such as check valves or injection ports. As a result, the chemical injection systems may become compromised and may require costly downhole retrieval and re-deployment. Moreover, the yield rating of materials used in the rupture mechanism (typically, metal) may change by temperature fluctuations in the downhole environment. As a result, the rupture mechanism may not yield at the expected fluid pressure because the downhole temperature has altered the yield rating. Therefore, the pressure test system may activate prematurely, thus requiring costly retrieval and re-deployment.